Various type of interleaved friction plate clutches having cooling means for the clutch plates have been proposed and used with certain degrees of success. An example of such cooling passage means is shown in U.S. Pat. No. 3,833,100 issued Sept. 3, 1974 and entitled "Control System for Power Transmission Clutch", and which is assigned to an assignee common with the present invention. That patent, as do many prior art structures, discloses a series of radially extending holes in the clutch hub which act to more or less haphazardly feed lubricating or cooling fluid to the clutch plates. However, due to the fact that the clutch plates are located at random locations with respect to the holes and furthermore due to the fact that these clutch plates are often slightly of non-flat or otherwise distorted shape lubricating fluid does not flow completely across all of the plates and in fact in many instances, certain spots on the clutch plates are completely dry. This results in overheating and burning up of the clutch plates.
Uniform distribution of fluid across the plates may be achieved by the use of excess quantities of oil, but this is uneconomical and presents other problems. Furthermore, particularly in large diameter clutches, the amount of cooling fluid necessary to cool the clutches has become excessive due to the large number of cooling passages and due to the high pressure of the oil flowing through the small cooling and lubricating passages. As a result, the total fluid flow in such clutches is often in the neighborhood of many hundreds of gallons of fluid per minute.